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Motor starting case studies

A motor starting case study for any given electrical network can be performed by reducing the network to a smaller equivalent network consisting of a source (generator/grid), the starting motor (largest motor), another large running motor, and a lumped load. This MS Excel-based spreadsheet is based on this concept and presents a small model of an electrical network that can be adapted for such motor starting case studies.

Motor starting calculation (MS Excel Spreadsheet)
Motor starting calculation (MS Excel Spreadsheet)

This is very helpful especially for quick checks as follows:

  1. What is the largest motor size that can be started with a given generator rating
  2. What should be the rating of the generator (or nos of generator operated in parallel) for a given load and largest motor size
  3. Knowing voltage drop during starting conditions for given motor details and hence deciding the key parameter during design (say max allowable starting current)
  4. Deciding the cable size/number of runs etc.

The spreadsheet performs an iterative calculation based on pre-start load inputs and starting motor data. The detailed analysis may be performed with the help of available software.


Notes:

  1. Motor starting analyses are generally performed for the largest motor connected to a switchboard.
  2. For worst-case results, motor starting analyses are generally performed considering the weakest source.
  3. Considering the above two facts, any given electrical network, where a starting analysis of a motor is required, can be reduced to a simplified network consisting of a source (generator/s or grid), the starting motor (largest motor), the running motor/s (second largest motor/s or motor of the same rating as the largest motor understudy) and other loads lumped together.
  4. Modeling
    This spreadsheet allows the user to model a given network as follows:

    1. Generator/s: The details of one generator shall be entered. If there is more than one generator of identical rating, these can be modeled simply by entering the number of the generator in parallel.
    2. Grid: The details of the grid shall be entered
    3. Transformer/s: The details of one transformer shall be entered. If there is more than one transformer of identical rating, these can be modeled simply by entering the number of the transformer in parallel.
    4. The spreadsheet considered either the “Generator/s” or the “Grid” supply for the motor starting the analysis. The “source for the motor starting analysis” can be selected via the drop-down menu. The selection automatically simulates switching “ON” or “OFF” the respective source breaker.
    5. Starting Motor: The details of the largest motor connected to the switchboard shall be entered.
    6. Running Motor/s: The details of the second largest running motor/s (or motor of rating same as the starting motor) connected to the switchboard shall be entered. This model can also be utilized by the user to check the voltage drop at the terminals of any remote motor/s.
    7. Lumped Load: The details of the remaining load on the switchboard can be modeled as a lumped load. The % motor can be defined which shall be modeled as constant power load while the remaining % of load shall be modeled as constant impedance load for the calculation.
    8. Error in data entry of the “voltage” input shall be highlighted if bus voltages are much different from the generator terminal voltage input of transformer voltage ratio inputs.

The excel spreadsheet has 2 sheets as follows:

  • Sheet title “Preface” with notes explaining the calculation spreadsheet and the summary about the software and
  • Sheet title ” Motor starting calculation” where actual data entry and calculations can be performed
Software:Motor Starting Calculation
Version:1.0
Developer:Hemant Kashikar
Size:104 Kb
Price:
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Motor Starting Calculation
Motor Starting Calculation

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49 Comments


  1. terry mulligan
    Nov 09, 2023

    How can I get a copy of the Motor Start calculator spread sheet please?


  2. Marco Iezzi
    Sep 04, 2023

    Hi I’am interested in this case study. How do I download it?


  3. khalid Naeim
    Sep 04, 2023

    Thank you very much for your effort.

    Please can I get free download?

    Best Wishes


  4. Khulekani Nyathi
    Mar 13, 2023

    interested in formulae


  5. Awel
    Nov 26, 2022

    Can I get free download?


  6. kumar swamy G
    Sep 10, 2022

    i needed calculation chart and course


  7. Dennis Taal
    Jun 04, 2022

    I find your program very informative and solution to basic designing. Thank you.


  8. Fabian Dulay
    Apr 28, 2022

    Pls share the excel password


  9. Edgardo Ramirez
    Apr 27, 2022

    I am interested on this motor starting case study.


  10. Jan Roets
    Nov 27, 2021

    Good Day Hemant

    Thank You for this information.
    I am not on your level regarding this, but I am going to try and use this to do calculation for an small open cast mine with about 50 380v motors of different size.
    Thank You
    Jan


  11. CALIXTO Morales Bantayan
    Aug 10, 2021

    How much the cost of your excel program?


  12. mokhtr
    Mar 31, 2021

    how calculator eaffact transient vacuum circuit large indction motor 1100kw 11kv and how calculator all parmater


  13. Kaushal Bhagat
    May 17, 2020

    This excel is password protected. Can u share the password to open this file


    • khalid Naeim
      Mar 28, 2023

      Thanks for your excellent effort.
      Please I need copy of this calculation
      Best Wishes


  14. Ram Prakash Sharma
    Sep 11, 2019

    Service provider


  15. Fairoz Ahamed
    Sep 02, 2019

    Dear Sir,
    It’s asking password for while opening the file. Please help…


  16. Durgaiah Sangepu
    Sep 02, 2019

    This excel is password protected. Can u share the password to open this file.


  17. RatnaKumar
    Jul 18, 2019

    Kindly send sample sheets.


  18. Alpha king
    Feb 20, 2019

    Good souces!Thanks!


  19. Khaled Ellithy
    Jan 25, 2018

    Thanks; Excellent for VDIP due to large motor starting;


  20. Khaled Ellithy
    Jan 25, 2018

    Thanks to you all. I have got a lot of useful materials in power systems area for my students

    Professor
    Ellithy


  21. Musse Mohamud Ahmed
    Jan 05, 2018

    Very good arrangements Guys, thank you very much.


  22. bhavin patel
    Dec 10, 2016

    dear sir
    can u please send me a detail example for the above excel sheet


  23. Vikram
    Jul 05, 2016

    Its an awesome workout and very useful.


  24. ANIL
    Feb 14, 2016

    Could not enter value generator voltage 6600 v for solo generator mode


    • PIERO VERCELLINO
      Mar 30, 2019

      Dear Sirs,
      many thanks to share your knowledge
      On excel file i can’t change selection from main grid to generator grid (generator ON grid OFF)
      Could you please help me

      Thanks

      Piero Vercellino


  25. FELIX JR.
    Feb 14, 2016

    THIS IS GOOD EXCEL PROGRAM IN THE CALCULATION OF % VOLTAGE STARTING DIP WHEN A LARGE MOTOR IS TARTED SUDDENLY EVEN WHEN ALREADY THERE’S EXISTING LOADS RUNNING.


  26. Boomi
    May 13, 2015

    Very much informative and I like all spreadsheets
    Thanks for uploading.
    Regards,
    Boomi


  27. Jason Buda
    Apr 21, 2015

    The excel spreadsheet downloaded just fine for me… It is very involved and I am looking forward to picking at it to fully understand how to use it. The introduction sheet seems very intuitive! Thanks for sharing!


  28. Abdulwahid
    Jan 15, 2015

    unable to download the excel sheets


  29. Rakesh Dhedhi
    Sep 11, 2014

    Dear Sir / Ma’am,
    First of all thanks for making such beautiful site for electrical world.

    Problem:
    In Electrical software, download file option it gives following errors while downloading file:
    1. By right click option : It saves html page instead of excel or other file.
    2. By box.com : We’re sorry, the server encountered an unexpected error.

    I hope admin will rectify this problem asap.
    Thanking you in anticipation.

    With best Regards,
    Rakesh Dhedhi
    Electrical Engineer


  30. Denis Milton
    Aug 27, 2014

    Motor Starting Calculation-Rev1.xls

    We’re sorry, the server encountered an unexpected error.


  31. VICTOR RAUTA
    Aug 26, 2014

    INTERESTING ENGAGEMENT,
    LOVING IT


  32. Melvin
    Jul 16, 2014

    unable to download the excel sheets


  33. Alfredo Labung
    Mar 28, 2014

    keen to know more about articles, software, guides & lectures of EEP tech refs as well…


  34. Nitin
    Feb 21, 2014

    Not able to download excel sheets…plz help


  35. nandaarief
    Nov 19, 2013

    thanks a lot, its very helpfull


  36. saunak
    Sep 23, 2013

    This site is really excellent i m very thankfull…it can be change my life electrical engineering….
    thank you soo much eep.


  37. Ashraf
    Jul 25, 2013

    I am not able to download the excel sheet


  38. karthikeyan
    Apr 09, 2013

    hi guys.. i am fresher to engineering…
    i would like to learn how motor starting calculation is done.
    please send me some technical articles/books in this regard to y mail id ([email protected])
    thanks in advance.


  39. WillG72
    Mar 02, 2013

    I cannot download either. I did as you advised about clearing the cache. When I click on ‘Download’, I am taken to a preview page called ‘Box’ and states that I need to login to it. I never heard of this and why do I need to login to some other site?
    William


  40. munis.munnu
    Oct 29, 2012

    i am not able to download the excel sheet….


  41. natemp
    Jul 03, 2012

    The worksheet not producing resuts for the below combination (even though this is not praticle)
    Transformer for voltage rating 11/0.2kV
    All loads with 0.2kV
    V2 bus voltage 0.2kV

    Please advise how to over come this issue

    thanks


  42. mpsaxena2003
    Nov 01, 2011

    I have made a vba macro in MS Excel for Transformer Sizing .I want to upload it in this site. How i do it.


  43. ajay34
    Aug 17, 2011

    why i cant download.. Motor Starting Calculation…

    even i had log in


    • Edvard
      Aug 17, 2011

      Logout and clear the cache in your browser and then login again. It should work. There was some works and improvements on EEP, so try to clear your cache.

      BR


      • WillG72
        Mar 02, 2013

        Back again. —- I am new to this and my first time trying to download. I have tried to access other downloads and, apparently, I cannot download anything because it takes me to another website called ‘Box’ and I need to download again! Do I need to have a ‘Box’ account, also? If so, this should be noted and clarified on the very first download page. I feel stupid for not knowing how to do a simple download that I have signed up for. Please give me simple instructions that actually fit the program.
        W.G.

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